1. Field of the Invention
The present invention relates to a power saving mode in an image forming apparatus, more particularly, to a technique for setting a power saving mode access time in an image forming apparatus.
2. Description of the Related Art
Generally, an image forming apparatus having a power saving mode, effects the power saving mode by cutting off unnecessary power when a user does not use the apparatus. The image forming apparatus automatically effects the power saving mode when a specific time has passed without an image being formed in the image forming apparatus. The specific time is referred to as a power saving mode access time.
The power saving mode access time is generally set by estimating a user's own image forming tendency and by using an operating panel of the image forming apparatus. Alternatively, a printer control plate of a host computer is used for setting the power saving mode access time. However, the image forming tendency may be changed for the user's business or for other reasons. At this time, the user may reset the power saving mode access time. However, when the image forming tendency is slightly changed, the user may not recognize it himself. Moreover, it is cumbersome for the user to reset the power saving mode access time whenever the image forming tendency is changed, even when the user recognizes it. Accordingly, the user uses an earlier power saving mode access time as is. However, there are problems in using the earlier power saving mode access time. For example, the problems are as follows.
In an earlier technique, a predetermined power saving mode access time is set to five minutes when an image is formed once an hour. This is to reduce electrical power consumption by promptly accessing the power saving mode since the image is formed every hour. However, when the image is formed every ten minutes due to a change of the image forming tendency, the user has to wait for a wake-up time of the image forming apparatus whenever printing is performed since the image forming apparatus accesses the power saving mode every five minutes. The wake-up time is for converting the power saving mode to a status for enabling the image forming apparatus to perform the image forming operation.
In another earlier technique, the power saving mode access time is set to thirty minutes when an image is formed every twenty minutes without waiting the wake-up time. However, when the image is formed every two hours due to a change of the image forming tendency, the image forming apparatus is unnecessarily in a wake-up status, causing an increased power consumption.
The earlier techniques for setting the power saving mode access time in the image forming apparatus as mentioned above, have problems, in which they fail to cope with a change of the user's printing tendency appropriately to the extent that the user does not reset the power saving mode access time by himself, causing an increased energy consumption or causing the user to wait for a wake-up time of the image forming apparatus whenever printing is performed. Also, such problems occur in the case of changing the user operating the image forming apparatus.
The patent to Nakamura et al., U.S. Pat. No. 5,321,478 entitled Image forming Apparatus Which Can Discriminate Frequency Of Image Forming Operations, discloses a system which sets the predetermined time period of the electric power reduction unit variably in accordance with the frequency of image forming operations discriminated by the discriminating unit.
The patent to Pearce et al., U.S. Pat. No. 5,617,572 entitled System For Reducing Power Consumption In Computers, discloses a system which adjusts the frequency with which timer interrupts are generated after the expiration of each time period.
The patent to Stewart et al., U.S. Pat. No. 5,566,340, entitled Portable Computer System With Adaptive Power Control Parameters, discloses a system in which the inactivity period required for entering a stand-by mode is varied in accordance with the user demands.
The Kikinis et al. patent, the Bajorek et al. patent, and the Douglis et al., patent, U.S. Pat. Nos. 5,542,035, 5,452,277, and 5,493,670, respectively entitled, Timer-Controlled Computer System Shutdown And Startup, Adaptive System For Optimizing Disk Drive Power Consumption, and Adaptive Disk SPN-Down Method For Managing The Power Distributed To A Disk Drive In A Laptop Computer, also disclose systems in which the stand-by state time period is varied in accordance with the user's requirements.
The following additional patents each disclose features in common with the present invention but are not as pertinent as the patents discussed in detailed above: the Nagasaka patent, U.S. Pat. No. 5,241,349 entitled Image Forming Apparatus Having A Plurality Of Control Modes Of Thermal Fixing Apparatus, the Dornier patent, U.S. Pat. No. 5,489,935 entitled Laser Printer Power Saver, and the Lee et al. patent, U.S. Pat. No. 5,589,923 entitled Power Saving Method of An Image Forming Apparatus.
While each of the aforecited patents has features in common with the present invention, none of them teaches the specifically recited technique for setting the power saving mode access time in accordance with the specifically recited equations of the present invention.